U.S. patent number 4,876,708 [Application Number 07/112,927] was granted by the patent office on 1989-10-24 for cordless telephone system.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba, NEC Corporation, Nippon Telegraph and Telephone Corp.. Invention is credited to Toshihiro Hara, Syoji Huse, Ryoji Kawasaki, Koji Ono, Noboru Saegusa, Kazuyuki Tate.
United States Patent |
4,876,708 |
Saegusa , et al. |
October 24, 1989 |
**Please see images for:
( Certificate of Correction ) ** |
Cordless telephone system
Abstract
A cordless telephone system includes a connector connected to a
subscriber telephone line and at least one radio telephone set
through a radio channel to establish or hold a communication
channel between the ratio telephone set and a subscriber. The
connector includes a control unit incorporating a timer. The
control unit sets the system in a self hold state in which the
radio channel is kept connected or a complete hold state in which
the radio channel is disconnected on the basis of a hold signal
from the radio telephone set, the presence/absence of a radio
reception signal within a predetermined period of time preset in
the timer, and the type of reception signal.
Inventors: |
Saegusa; Noboru (Tokyo,
JP), Hara; Toshihiro (Tokyo, JP), Kawasaki;
Ryoji (Tokyo, JP), Tate; Kazuyuki (Aichi,
JP), Huse; Syoji (Tokyo, JP), Ono; Koji
(Tokyo, JP) |
Assignee: |
NEC Corporation (Tokyo,
JP)
Nippon Telegraph and Telephone Corp. (Tokyo, JP)
Kabushiki Kaisha Toshiba (Kanagawa, JP)
|
Family
ID: |
17324493 |
Appl.
No.: |
07/112,927 |
Filed: |
October 27, 1987 |
Foreign Application Priority Data
|
|
|
|
|
Oct 30, 1986 [JP] |
|
|
61-258745 |
|
Current U.S.
Class: |
455/462; 379/162;
379/393 |
Current CPC
Class: |
H04M
1/72513 (20130101) |
Current International
Class: |
H04M
1/72 (20060101); H04M 1/725 (20060101); H04M
011/00 (); H04M 001/00 () |
Field of
Search: |
;379/61-62,57-58,63,159,160,162-163,393 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
4640987 |
February 1987 |
Tsukada et al. |
4650931 |
March 1987 |
Tsukada et al. |
4706274 |
November 1987 |
Baker et al. |
|
Primary Examiner: Ng; Jin F.
Assistant Examiner: Kim; David H.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak &
Seas
Claims
What is claimed is:
1. A cordless telephone system comprising at least one radio
telephone set, a subscriber line connected through a telephone
exchanger to a subscriber telephone set, and connector means,
connected to said at least one radio telephone set through a radio
channel and to said subscriber line and having a function for
establishing a communication channel between said at least one
radio telephone set and said subscriber telephone set and a
function for holding said communication channel in response to a
hold signal from said at least one radio telephone set, wherein
said connector means comprises:
first hold state setting means for setting said communication
channel in a first hold state without disconnecting said radio
channel in response to the hold signal received upon establishment
of said communication channel;
first determining means for determining the presence/absence of a
radio reception signal within a first predetermined period of time
after the first hold state is initiated;
hold state releasing means for releasing the first hold state and
reconnecting the communication channel when the radio reception
signal received at first within the first predetermined priod of
time is the hold signal in accordance with a determination result
of said first determining means;
second hold state setting means for disconnecting said radio
channel and setting said communication channel in a second hold
state when the radio reception signal received at first within the
first predetermined period of time is an on-hook signal or the
radio reception signal is not received within the first
predetermined period of time, in accordance with the determination
result of said first determining means;
second determining means for determining the presence/absence of
the radio reception signal within a second predetermined period of
time after the second hold state is initiated;
hold state changing means for changing the second hold state to the
first hold state when the radio reception signal received within
the second predetermined period of time is an off-hook signal, in
accordance with a determination result of said second determining
means; and
circuit control means for forcibly disconnecting said communication
channel and setting said communication channel in a stand-by state
when the radio reception signal is not received within the second
predetermined period of time, in accordance with the determination
result of said second determining means.
2. A cordless telephone system comprising at least one radio
telephone set, a subscriber line connected through a telephone
exchanger to a subscriber telephone set, and connector means,
connected to said at least one radio telephone set through a radio
channel and to said subscriber line and having a function for
establishing a communication channel between said at least one
radio telephone set and said subscriber telephone set and a
function for holding said communication channel in response to a
hold signal from said at least one radio telephone set,
wherein said connector means comprises
radio transmitting/receiving means connected to said radio
channel,
control means, incorporating a timer, for controlling operations of
said connector means in response to various signals received from
said at least one radio telephone set through said radio
transmitting/receiving means,
holding tone generating means, controlled by said control means,
for generating a holding tone signal representing a hold state,
and
switching means, controlled by said control means, for connecting
said subscriber line and said radio transmitting/receiving means
with each other to set a talking state when said communication
channel is established, and for connecting an output from said
holding tone generating means to said subscriber line and said
radio transmitting/receiving means in the hold state; and
wherein said control means controls
to cause said switching means to disconnect said subscriber line
from said radio transmitting/receiving means in response to the
hold signal from said at least one radio telephone set during
establishment of said communication channel and at the same time
cause said holding tone generating means to supply an output signal
to said subscriber line and said radio transmitting/receiving
means,
to set a first predetermined time to said timer and cause said
timer to start,
to keep connecting said radio channel to said radio
transmitting/receiving means, thereby initiating a first hold
state,
to switch said switching means to a talk position to release the
hold state when a radio reception signal received at first within
the first predetermined period of time after initiation of the
first hold state is the hold signal,
to disconnect said radio channel to set a second hold state when
the radio reception signal received at first within the
predetermined period of time is an on-hook signal or the radio
reception signal is not received within the first predetermined
period of time,
to set a second predetermined time in said timer and cause said
timer to start,
to change the second hold state to the first hold state in response
to a first off-hook signal received within the second predetermined
period of time in the second hold state, and
to inhibit a transmission function of said radio
transmitting/receiving means and set said radio
transmitting/receiving means in a stand-by state when the radio
reception signal is not received within the second predetermined
period of time.
3. A system according to claim 2, wherein said connector means
comprises display means, connected to said control means, for
displaying the first and second hold states.
4. A system according to claim 2, wherein said radio telephone set
comprises operation means for generating said hold signal, said
on-hook signal, and said off-hook signal.
5. A system according to claim 2, wherein said connector means
further comprises a handset connected to said subscriber line and
said radio transmitting/receiving means respectively through said
switching means and said control means.
6. A system according to claim 4, wherein said operation means
comprises a hold button for generating said hold signal, a talk
completion button for generating said on-hook signal, and a talk
button for generating said off-hook signal.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a cordless telephone system and,
more particularly, to a hold control system in a cordless telephone
system having a hold function.
As shown in FIG. 1, a conventional cordless telephone system having
a hold function comprises a plurality of radio telephone sets 1
having an identical arrangement, a connection apparatus or
connector 2 coupled to the radio telephone sets 1 via a radio
channel 3, and a subscriber telephone set 5 connected to the
connector 2 through a subscriber line 4 and a telephone exchanger
6.
Each radio telephone set 1 includes dial keys, a talk button, a
talk completion button, and a hold button. The connector 2 includes
a talk/hold switch for switching between the talk mode and the hold
mode, and a controller for controlling the operation of the
talk/hold switch.
FIG. 2 is a sequence diagram for explaining the hold control
operation of the cordless telephone system having a hold
function.
Referring to FIG. 2, vertical lines A, B, C, D, and E represent a
person or bearer using the radio telephone set 1, the radio
telephone set 1, the controller in the connector 2, the talk/hold
switch in the connector 2, and the subscriber telephone set 5 and
its bearer, respectively. The operation sequence progresses
downward in FIG. 2. Continuation of arrows represents a chain of
operations of portions A to E which are caused by one operation by
the radio telephone set bearer A.
When a communication channel is being established and talking is
performed between the radio telephone set 1 and the subscriber
telephone set 5 in an operation sequence and the radio telephone
set bearer A depresses the hold button in the radio telephone set 1
in a sequence b, a radio hold signal is transmitted from the radio
telephone set 1 to the connector 2. The controller in the connector
2 sends the hold signal to the talk/hold switch to set it in the
hold position. At the same time, holding tone or music is sent to
the subscriber telephone set 5. The communication channel is then
held in the hold state. When the radio telephone set bearer A
on-hooks the radio telephone set 1 in an operation sequence c, the
radio telephone set 1 outputs the hold signal to cause the
controller in the connector 2 to generate and send the holding
music to the subscriber telephone set 5. When the radio telephone
set bearer A off-hooks the radio telephone set 1 in an operation
sequence d, the radio telephone set 1 stops sending the hold
signal. In this case, the transmitter in the radio telephone set 1
transmits only a radio carrier signal. The controller in the
connector 2 sets the talk/hold switch in the talk position and
stops sending the holding music. As a result, the hold state of the
communication channel is set in the busy state in a sequence e.
In the conventional hold control system described above, the radio
channel is maintained even during the hold period. However, since
talking is not performed in the hold period, the radio channel need
not be maintained. This mode of operation is not preferable from
the viewpoint of effective utilization of radio or electric
waves.
In a system having a plurality of radio telephone sets 1, a demand
has arisen to allow an operation wherein the communication channel
held in the hold state by one radio telephone set, e.g., 1-(1) can
be released by another radio telephone set, e.g., 1-(2) to restart
talking. However, the demand cannot be satisfied.
SUMMARY OF THE INVENTION
It is an object of the present invention to eliminate the
conventional problems described above and to provide a cordless
telephone system capable of interrupting sending of an electric
wave in the hold state in which the radio channel need not be
maintained and capable of releasing the hold state from another
radio telephone set to restart talking.
In order to achieve the above object of the present invention,
there is provided a cordless telephone system comprising a
connector connected to a subscriber telephone set, and at least one
radio telephone set connected to the connector through a radio
channel, the at least one radio telephone set transmitting, through
the radio channel, to the connector a hold signal, an off-hook
signal, and an on-hook signal in response to depressions of a hold
button, a talk button, and a talk completion button,
respectively.
The connector has radio transmitting/receiving unit, a switching
unit, a holding unit and a control unit for controlling the
transmitting/receiving unit, the switching unit and the holding
unit in response to the hold signal, the off-hook signal, and the
on-hook signal to control the system such that; when the hold
signal is received after a communication channel is established,
the communication channel is set in a first hold state in which the
radio channel is kept connected; within a first predetermined
period of time after the first hold state is started, when the hold
signal is received or no radio reception signal is detected, the
communication channel is released, but when the on-hook signals is
received, the communication channel is set in a second hold state
in which the radio channel is disconnected; within a second
predetermined period of time after the second hold state is
started, when the off-hook signal is received, the communication
channel is changed from the second hold state to the first hold
state; and when a radio reception signal is not detected within the
second predetermined period of time, the communication channel is
forcibly disconnected and set in a stand-by state.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a configuration of a conventional
cordless telephone system;
FIG. 2 is a sequence diagram for explaining hold control operation
according to the prior art;
FIG. 3 is a block diagram of a radio telephone set used in a
cordless telephone system according to an embodiment of the present
invention;
FIG. 4 is a block diagram of a connector in the cordless telephone
system according to the embodiment of the present invention;
FIGS. 5, 6, 7, and 8 are sequence diagrams for explaining hold
control operation in the cordless telephone system according to the
present invention;
FIGS. 9(a) to 9(d) and 10(a) to 10(f) are timing charts of signals
for explaining the control operation of the present invention;
and
FIG. 11 is a flow chart for explaining the control operation of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will be described
with reference to the accompanying drawings.
The system configuration of the cordless telephone system according
to the present invention is the same as that in FIG. 1, and a
detailed description thereof will be omitted. The same reference
numerals as in FIG. 1 denote the same parts in the embodiment.
FIG. 3 is a radio telephone set 1 according to the embodiment of
the present invention. The radio telephone set 1 comprises a radio
transmitting/receiving unit 15, a control unit 16, an operation
unit 17, and a display unit 18. The radio transmitting/receiving
unit 15 is caused to maintain a radio channel 3 in a self hold
state (to be described later) by the control unit 16. However, in a
complete hold state (to be described later), the radio
transmitting/receiving unit 15 disconnects the radio channel 3. In
other words, the unit 15 stops transmitting a radio or electric
wave.
The operation unit 17 includes dial buttons 17-1, a talk button
17-2, a talk completion button 17-3, and a hold button 17-4. The
control unit 16 generates a signal corresponding to the button
operations and the signal is transmitted to a connector 2 through
the radio transmitting/receiving unit 15 and the radio channel
3.
An off-hook signal is generated upon operation of the talk button
17-2, an on-hook signal is generated upon operation of the talk
completion button 17-3, and a hold signal is generated upon
operation of the hold button 17-4, in the same manner as in the
conventional techniques.
The display unit 18 comprises a hold indicator lamp 18-1 and other
lamps (not shown). The hold indicator lamp 18-1 indicates that the
radio telephone set 1 is held in the self hold state by the control
unit 16. The hold indicator lamp 18-1 is turned off by the control
unit 16 when the complete hold state is set. The control unit 16 is
connected to a handset 16-1 and a speaker 16-2 for producing a
ringing tone. The speaker 16-2 is controlled to generate a hold
alarm tone when the bearer forgets to reset holding.
FIG. 4 shows an arrangement of the connector 2. Referring to FIG.
4, the connector 2 comprises a switching unit 21, a holding music
generating unit 22, a control unit 23, a handset 24, an operation
unit 25, a radio transmitting/receiving unit 26, and a display unit
27. The radio transmitting/receiving unit 26 holds the radio
channel 3 in the self hold state. In the complete hold state, the
transmitting/receiving unit 26 disconnects the radio channel 3. In
other words, the unit 26 stops transmitting an electric wave.
The holding music generating unit 22 generates a holding tone
(e.g., holding music) in the self and complete hold states to be
described later and sends the holding tone to the switching unit
21.
The switching unit 21 switches a subscriber telephone line 4 in the
talk or hold mode under the control of the control unit 23. When
the communication channel is formed between the radio telephone set
1 and the subscriber telephone set 5, the switching unit 21
connects the subscriber telephone line 4 to the radio
transmitting/receiving unit 26. In the self hold state, the
switching unit 21 connects the holding music generating unit 22 to
the subscriber telephone line 4 and the radio
transmitting/receiving unit 26. In the complete hold state, the
switching unit 21 connects the holding music generating unit 22 to
the subscriber telephone line 4.
The operation unit 25 includes dial buttons 25-1, a hook switch
25-2, a hold button 25-3, and other buttons (not shown). Signals
corresponding to these switches are input to the control unit
23.
The display unit 27 includes a hold indicator lamp 27-1 and other
lamps (not shown) in the same manner as in the lamp 18-1 in the
radio telephone set 1. The hold indicator lamp 27-1 indicates the
self or complete hold state. The self and complete hold states are
indicated by different modes, e.g., continuous lighting and
flickering.
The control unit 23 establishes the communication channel between
the connector 2 and the subscriber telephone set 5 connected to the
subscriber telephone line 4, or between the radio telephone set 1
and the connector 2 through the radio channel 3. At the same time,
the control unit 23 performs hold control by using a timer 28. The
control unit 23 sets the communication channel in the self hold
state without disconnecting the radio channel 3 in response to the
hold signal received after the communication channel is connected
with the radio telephone set 1. The control unit 23 then monitors
the presence/absence of the radio signal received within a
predetermined period of time by using the timer 28 after the self
hold state is initiated. When the radio signal received at first
within the predetermined period of time is the hold signal, the
control unit 23 controls the switching section 21 to release the
self hold state and engage the communication channel with the radio
telephone set 1 again. However, when the first radio signal
received within the predetermined period of time is an on-hook
signal, or when the signal is not received within the predetermined
period of time, the control unit 23 controls the radio
transmitting/receiving unit 26 to disengage the radio channel from
the radio telephone set 1. In other words, the control unit 23
causes the radio transmitting/receiving unit 26 to stop
transmitting the electric wave and set the communication channel in
the complete hold state. Thereafter, by using the timer 28, the
control unit 23 monitors the presence/absence of a radio signal
received within a predetermined period of time after the complete
hold state is initiated. If a radio signal received within this
predetermined period of time is an off-hook signal, the control
unit 23 controls the radio transmitting/receiving unit 26 to change
the complete hold state to the self hold state. However, when the
radio signal is not detected within this second predetermined
period of time, the control unit 23 forcibly disconnects the
communication channel.
The hold control operation of the cordless telephone system
according to this embodiment will be described with reference to
FIGS. 5 to 11.
In the sequence diagrams shown in FIGS. 5 to 8, vertical lines A,
B, C, D, and E represent a bearer of the radio telephone set 1, the
radio telephone set 1, the control unit 23, the switching unit 21
and the holding music generating unit 22 in the connector 2, and
the subscriber telephone set 5, respectively.
Referring to FIG. 5 and FIG. 11, in an operation sequence a, the
connector 2 establishes the communication channel between the radio
telephone set 1, e.g., 1-(1) through the radio channel 3 and the
subscriber telephone set 5 through the subscriber telephone line 4.
Talking is thus performed between a bearer A of the radio telephone
set 1 and a subscriber of the subscriber telephone set 5 (step 110
in FIG. 11). When the bearer A depresses the hold button 17-4 in
the radio telephone set 1 in an operation sequence b, the control
unit 16 in the radio telephone set 1 generates a hold signal H. An
identification number (ID) of the self telephone set 1 is added to
the hold signal H, and the composite signal is sent to the
transmitter in the radio transmitting/receiving unit 15. At the
same time, the hold indicator lamp 18-1 in the display unit 18 is
turned on. The hold signal H is transmitted to the connector 2
through the radio channel 3.
Since the first radio signal received during talking is the hold
signal H (step 111 in FIG. 11), the control unit 23 in the
connector 2 which receives the hold signal H initiates the timer
28, the switching unit 21, and the holding music generating unit
22. The switch in the switching unit 21 is switched to the hold
position to set the communication channel in the hold state. At the
same time, the holding music is transmitted to the subscriber
telephone line 4 and the radio telephone set 1. The radio channel 3
is kept connected. This state (step 112 in FIG. 11) is the self
hold state. Time lapse in the self hold state is monitored by the
timer 28.
In the self hold state, even if the connector 2 and other radio
telephone sets 1, e.g., 1-(2), 1-(3), . . . are off-hooked for a
call, the control unit 23 in the connector 2 does hot accept such a
call request. Calls excluding the one kept in the hold state cannot
therefore be connected. The self hold state, i.e., the state in
which the radio channel is kept connected, cannot be released by
other radio telephone sets. This operation is the same as the
conventional hold state.
FIG. 6 shows an operation for releasing the self hold state.
Referring to FIG. 6 and FIG. 11, in the self hold state in an
operation sequence a, when the bearer A of the radio telephone
state 1 depresses the hold button 17-4 in order to release the self
hold state within a predetermined set time of the timer 28 in an
operation sequence b, the control unit 16 detects the operation of
the hold button 17-4 (step 113 in FIG.11) and sends the hold signal
H including the ID number. As shown in step 114 in FIG. 11, the
control unit 23 in the connector 2 receives the hold signal H and
causes the switching unit 21 to switch from the hold position to
the talk position since the first signal received after holding of
the communication channel is a hold signal H. At the same time, the
control unit 23 causes the holding music generating unit 22 to stop
generating holding music. The timer 28 is reset, and the hold
indicator lamp 27-1 is turned off. Talking can be performed in an
operation sequence c.
FIG. 7 and step 11b in FIG.11 show an operation when the bearer A
changes the radio telephone set 1-(1) to another radio telephone
set, e.g., 1-(2). In an operation sequence a, the radio telephone
set 1-(1) is set in the self hold state, and then the bearer A
depresses the talk completion button 17-3 of the radio telephone
set 1-(1) within a time preset in the timer 28, i.e., on-hook
operation, in an operation sequence b. The control unit 16 in the
radio telephone set 1-(1) sends out an on-hook signal I including
the ID number thereof. The control unit 23 in the connector 2
receives the on-hook signal I and transmits a talk completion
signal J to the radio telephone set 1-(1) and causes the
transmitter in the radio transmitting/receiving unit 26 to stop
transmitting the electric wave. The timer 28 is reset. The radio
telephone set 1-(1) which receives the talk completion signal J
causes the transmitter in the radio transmitting/receiving unit 15
to stop transmitting the electric signal. In other words, the radio
channel is disengaged from the radio telephone set 1-(1) and set in
the hold state wherein the radio channel is not connected thereto,
i.e., the complete hold state.
In the complete hold state, the hold indicator lamp 18-1 in the
radio telephone set 1-(1) is turned off, and the hold indicator
lamp 27-1 in the connector 2 is turned on to indicate the complete
hold state.
In the complete hold state, any radio telephone set including the
radio telephone set 1-(1) can make a call and release the hold
state of the communication channel. Even in this complete hold
state, the holding music is sent to the subscriber telephone set
5.
FIG. 8 and step 117 in FIG. 11 show an operation for releasing the
complete hold state of the communication channel by a call from any
radio telephone set 1, for example 1-(2), in the complete hold
state. The bearer of the radio telephone set 1-(2) depresses the
talk button 17-2 of the radio telephone set 1-(2) to release the
hold state, i.e., off-hook operation in an operation sequence a.
The control unit 16 in the radio telephone set 1-(2) then sends a
calling signal K including the ID number thereof, and the hold
indicator lamp 18-1 is turned on. The control unit 23 in the
connector 2 transmits a calling response signal to the
corresponding radio telephone set 1-(2). As a result, the radio
channel 3 is formed between the radio telephone set 1-(2) and the
connector 2, and the self hold state is set.
Since the radio telephone set 1-(2) is set in the self hold state,
the hold indicator lamp 18-1 is turned on. Therefore, the bearer of
the radio telephone set 1-(2) can talk to the subscriber by
depressing the hold button 17-4 (FIG. 6).
An operation will be described wherein the communication channel is
disengaged from the radio telephone set 1 and the radio telephone
set 1 is set in the stand-by state when the self or complete hold
state continues for a long period of time.
Referring to FIGS. 9(a) to 9(d), the control unit 23 in the
connector 2 receives the hold signal H from the radio telephone set
1 at time TT0. The self hold state is set at time TT1, and at the
same time the timer 28 is operated. When the hold signal H from the
radio telephone set 1 is not received before time TT2 at which the
time interval T1 set in the timer 28 elapses, a hold alarm signal N
is transmitted through the radio channel 3. The control unit 16 in
the radio telephone set 1 receives the hold alarm signal N and
generates a hold alarm AL in response to the signal N. The control
unit 23 in the connector 2 stops transmitting the hold alarm signal
N at time TT3 and causes the timer 28 to start. When a time T2
preset in the timer 28 has elapsed at time TT4, the hold alarm
signal N is sent to the radio telephone set 1 again. The control
unit 16 in the radio telephone set 1 receives this hold alarm
signal N and generates the hold alarm AL in response to the signal
N again. If the control unit 23 in the connector 2 cannot receive
the hold signal H from the radio telephone set 1 before time TT5,
the radio channel 3 is disengaged from the radio telephone set 1,
and the complete hold state is initiated.
Referring to FIGS. 10(a) to 10(f), the control unit 23 in the
connector 2 receives the hold signal H from one radio telephone
set, e.g., 1-(1) at time TT1. The control unit 23 receives an
on-hook signal I at time TT3 and is set in the complete hold state.
At the same time, the timer 28 is started. When holding is not
released before time TT4 at which the time preset in the timer 28
elapses, the control unit 23 transmits the hold alarm signal N to
all the radio telephone sets 1-(1), 1-(2), . . . over an exclusive
radio control channel in order to signal to them that holding is
continued for a long period of time. The control units 16 of the
radio telephone sets which receive the hold alarm signal N generate
the hold alarm AL in response to the hold alarm signal N. The
control unit 23 in the connector 2 stops transmitting the hold
alarm signal N at time TT5. At the same time, the timer 28 is
started. When the time preset in the timer 28 has elapsed again at
time TT6, the control unit 23 generates the hold alarm signal N
again. The control units 16 in the radio telephone sets 1 which
receive the hold alarm signal N generate the hold alarm AL in
response to the hold alarm signal N again. When holding of any of
the radio telephone sets 1 is not released before time TT7 (step
118 in FIG. 11), the communication channel kept in the hold state
is forcibly disconnected, and the stand-by state is set (steps 119
and 120 in FIG. 11).
The operations described in FIGS. 9(a) to 9(d) and 10(a) to 10(f)
are not independent operations but may be a series of operations.
For example, when the self hold state is released upon the lapse of
the predetermined period of time and the complete hold state is
set, and when the complete hold state is released, the
communication channel kept in the hold state is forcibly
disconnected and is set in the stand-by state.
According to the cordless telephone apparatus described above, the
hold control system for forcibly holding and disconnecting the
communication channel is a system capable of performing holding
while the radio channel is disconnected. Therefore, during holding
which does not require talking, transmission of the electric wave
can be stopped, thereby effectively utilizing the electric
wave.
Furthermore, when a plurality of radio telephone sets are used, the
call held by a given radio telephone set can be released from any
other radio telephone set according to the will of the bearer of
the given radio telephone set, thereby providing a convenient
cordless telephone system.
Furthermore, according to the present invention, even if the bearer
forgets to release holding while the radio channel is connected,
the radio channel can be disengaged from the radio telephone set,
thereby more effectively utilizing the electric wave.
* * * * *